Cauliflower (Brassica oleracea L.) Seed Vigour: Imbibition Effects

By means of a machine vision facility, the process of water-imbibitionin a small seeded brassica species was recorded as the visibleincrease in seed volume. Dry cauliflower seed (Brassica oleracea)showed an immediate rapid phase of imbibition upon the additionof water. This initial phase was associated with the reductionin seedling root growth resulting from the imbibition of coldwater, and the rate of uptake of water at 20?C was negativelycorrelated with subsequent seedling growth. Damage to the testaof dry seed resulted in an increased rate of imbibition anda corresponding decrease in seedling root growth measured onslant boards. This showed that the intact testa of cauliflowerseed is capable of acting as a barrier to water influx and thata high rate of water uptake is damaging to the embryo. Testadamage reduced percentage soil emergence of seeds, as did raisingthe soil moisture content during the imbibition period by wateringimmediately after sowing. Both these treatments were believedto increase imbibition rate. Conditions which encouraged a lowrate of water uptake also improved the rate and uniformity ofemergence. Correlation of mean imbibition rates (measured ina laboratory test) with soil-emergence indicated that the sensitivityto imbibition damage varied between seed lots and interactedwith the absolute rate of water influx to determine the finalpercentage emergence. This factor prevented reliable predictionof seedling performance from the ranked-order of measured imbibitionrates. The significance of these findings to the seed productionand modular transplant raising industries is discussed. Key words: Machine vision, imbibition rate, testa, soil moisture, vigour